PR24955, libbfd terminating program on out of memory

PR24955, libbfd terminating program on out of memory

This patch fixes the worst of the cases where libbfd might terminate
a program due to calling xstrdup or xmalloc.  I've also fixed some
error paths that didn't clean up properly.

	PR 24955
	* libbfd-in.h (bfd_strdup): New inline function.
	* archive.c (_bfd_get_elt_at_filepos): Use bfd_strdup.  Close
	bfd on error.
	* elfcode.h (_bfd_elf_bfd_from_remote_memory): Use bfd_strdup.
	* opncls.c (bfd_fopen): Use bfd_strdup.  Close fd and stream
	on error.
	(bfd_openstreamr): Use bfd_strdup.
	(bfd_openr_iovec, bfd_openw, bfd_create): Likewise.
	* plugin.c (try_load_plugin): Use bfd_malloc.
	* libbfd.h: Regenerate.